yah, i use stainless bolts on mine for the plates. i dont run the stillen bracket btw.
GJ on painting the screw heads, that should make them last a while. i do this on the pan screws in the wheelwells (splashguards/bumper). i hate rusted bolt heads. just unscrew a little bit so the heads are off the plastic, and clean and paint, let dry over night. screw it back in. no need to remove the screw completely off the car for these.